'Tehran should not be allowed to use the nuclear deal as a bargaining tool and “hold the world hostage,” the US ambassador to UN has said after Iran's president Hassan Rouhani warned that Tehran could backtrack on the 2015 agreement “within hours” should new sanctions be imposed.“Iran cannot be allowed to use the nuclear deal to hold the world hostage. The nuclear deal must not become too big to fail,” Nikki Haley said in response to Rouhani’s remarks.

On Tuesday, Rouhani told a session of parliament, broadcast live on state television, that if Washington goes back to its practice of imposing unilateral sanctions, then “Iran would certainly return in a short time – not a week or a month but within hours – to conditions more advanced than before the start of negotiations.”'